Until now, there has widely been known substrate treatment apparatuses in which a process gas is activated by plasma discharge to give a treatment to a substrate. In such substrate treatment apparatuses, a high-frequency voltage is applied between plural discharge electrodes to generate plasma, which excites and activates the applied gas to perform such substrate treatment as forming a thin film on a substrate surface or performing etching.
However, for example, when a contaminant exists in a chamber, it causes the contamination of the substrate after the treatment, or, when a residual gas exists, an intended effect of the treatment can not be sufficiently obtained. Therefore, for the purpose of adjusting an atmosphere in the chamber prior to the substrate treatment, it is generally performed to introduce a gas that is used in the treatment into the chamber and to generate plasma for conditioning the inside of a vacuum chamber. The conditioning exerts such effect as stabilizing the atmosphere in the chamber, and stabilizing the substrate treatment performance. The conditioning is particularly effective when it is followed by a lot start or a change of the process gas.
Next, the conditioning will be described along with the difference between the conditioning and cleaning that is widely performed for plasma treatment apparatuses. The cleaning means removing impurities generated during the treatment process and making the inside atmosphere and the inner wall of the chamber in a clean state. On the other hand, the conditioning means introducing gas to be used for the process treatment of a semiconductor substrate into the chamber before giving the process treatment, and adjusting the atmosphere in the chamber by making active species, generated by discharging the gas, adhere to the chamber inner wall for the purpose of stabilizing the treatment rate and the film properties throughout a continuous treatment.
When the conditioning is not performed, the state of the chamber inner wall becomes vulnerable to the progress of the treatment and the treatment rate in the continuous processing becomes unstable. Further, if impurities adhere to the chamber inner wall, impurities can be contained in the film to deteriorate film properties. The conditioning is performed in order to improve these adverse effects. As a result, the treatment rate of the continuous treatment becomes stable, and good film properties are obtained.
Patent Document 1 discloses an example of such plasma treatment apparatus. FIG. 3 shows the plasma treatment apparatus in Patent Document 1. The method in Patent Document 1 performs effective plasma conditioning by adjusting an electrode interval upon the conditioning, even when the electrode interval is narrowed to enhance the etching rate.
That is, an electrode elevating mechanism 108 makes the position of an upper electrode 103 variable, and widens the interval between a lower electrode 102 and the upper electrode 103 upon the conditioning as compared with that upon the etching to allow the plasma to spread widely. And, it is designed so as to remove reaction products and the like adhered to a vacuum chamber 101, the lower electrode 102, the upper electrode 103 and the like.
However, Patent Document 1 adopts such construction as generating plasma using electrodes of a parallel flat plate. Consequently, even when the interval between the upper and lower electrodes is widened upon the conditioning to allow the plasma to spread widely, the conditioning is not sufficiently performed in other places, although the conditioning effect is large between electrodes.
As another example, there is a plasma treatment apparatus described in Patent Document 2. FIG. 4 shows the treatment apparatus in Patent Document 2. The method in Patent Document 2 performs rapidly and uniformly the plasma conditioning of the inside of a vacuum vessel of an ECR type microwave plasma treatment apparatus.
That is, high density radicals are generated in a vacuum chamber (a plasma generation chamber 203, a delivery chamber 211). And the position of a stage 208 is set so that the effective conditioning area can expand to the distance, at which the density of the radicals is reduced to half. Then a plasma cleaning using the radicals is carried out. Specifically, the conditioning is performed while setting the gas pressure to be 50 mTorr or more, and moving the stage 208 for placing an object to be treated within 130 mm from the ECR area. The Document describes that the conditioning can be performed rapidly and uniformly within the limited area.
Patent Document 2 describes that the conditioning is performed in a state where the stage lies within 130 mm from the ECR area, however, in the case of this condition, most of the area to be conditioned is the reaction chamber, and the conditioning may not be effective for a lower portion of the vacuum chamber (the conditioning efficiency deteriorates significantly).
[Patent Document]
[Patent Document 1] Japanese Patent Laid-Open No. 05-343372
[Patent Document 2] Japanese Patent Laid-Open No. 06-097130